GPT and leukemia: There are several hallmarks of the telomere length maintenance via ALT, including the following: (i) a long and heterogeneous telomere length [14, 19, 20, 54]; (ii) the presence of ALT-associated promyelocytic leukaemia (PML) nuclear bodies (APBs) [28, 54]; and (iii) the generation of high levels of C-rich circular telomeric DNA repeats (C-circles) [6, 22].